The present invention relates to a liquefied fuel vaporizing apparatus for vaporizing a liquefied fuel contained in a liquefied gas vessel and supplying the vaporized fuel to a gas engine.
FIG. 8 is a schematic view showing an example of a liquefied fuel supplying apparatus for a conventional gasoline engine. A 2-cycle engine B mounted on a portable work machine includes a crankcase 23 connected to the lower part of a cylinder body 20 having many cooling fins, a recoil starter 24 for starting the engine connected to the front end of a crankshaft (not shown) via a clutch, and a blower connected to the rear end of the crankshaft.
The blower, which is contained in a fan case 22 connected to the back of the cylinder body and crankcase 23, sucks outside air from the rear end of the crankshaft. The cooling air from the blower is sent from the back of the cylinder body to the front part of the engine through the spaces between the cooling fins. A suction port provided on the left-hand wall of the cylinder body 20 is connected to a mixer C via an insulating tube 17, and an exhaust port provided on the right-hand wall is connected to an exhaust muffler 21. Reference numeral 19 denotes a spark plug.
A liquefied gas vessel or cylinder 3, which is similar to a cylinder used for a household portable cooking stove or the like, is mounted under the engine B by a holder 2. The holder 2 has a fuel cock 5 and a fuel outlet 6 on the right-hand wall thereof.
The liquefied gas vessel 3 is mounted elastically between the left-hand and right-hand walls of the holder 2 so that a fuel suction pipe 3a is below the liquid level. When the fuel cock 5 is opened, the liquid fuel in the vessel 3 is supplied to the mixer C of the engine B through the fuel suction pipe 3a, fuel cock 5, and fuel outlet 6. When the temperature of outside air is low (lower than about 10), most of the fuel at the fuel outlet 6 is in a liquid state.
A vaporizer 7 for vaporizing the liquid fuel sent from the liquefied gas vessel 3 is disposed on the front wall (the opposite side to the blower attaching portion) of the cylinder body 20 of the engine B. The vaporizer 7, consisting of a metallic tube bent into a U-shape, is disposed in a substantially horizontal position in front of the cylinder body 20.
An inlet 7a at one end of the vaporizer 7 is bent downward and is connected by a pipe 6a to the fuel outlet 6 of the liquefied gas vessel 3. An outlet 7b at the other end of the vaporizer 7 is connected to an inlet 12 of a primary pressure governor A. The primary pressure governor A includes a diaphragm 10 held between a housing 13 and a bottom plate 13a so as to define a fuel chamber 11 on the upper side of the diaphragm 10 and an air chamber on the lower side thereof. The primary pressure governor A also includes a valve element 8 supported on the wall of the fuel chamber 11 by a shaft 14 which is connected to the diaphragm 10 by a rod. The valve element 8 is urged by the force of a spring 9 so as to open the inlet 12.
The fuel chamber 11 supplies fuel to a constant-pressure fuel chamber 38 of a secondary pressure governor E through an outlet 12a, a pipe 15, and an inlet passage 44a of the secondary pressure governor E. The secondary pressure governor E is integral with the mixer C and includes a valve element 44. The mixer C includes a suction air passage 36 passing through the body 35 and connected at one end to an air cleaner (not shown) and at the other end to the insulating tube 17. The body 35 incorporates a publicly known piston type throttle valve 37, which protrudes into the suction air passage 36 through the upper wall, for heating the fuel and air supplied to the engine. The throttle valve 37 has a needle valve that protrudes into a fuel passage 37a, described later. When the throttle valve 37 is slid vertically by an accelerator lever (not shown), the air in the suction air passage 36 is accelerated so that the fuel is sucked from the constant-pressure fuel chamber 38 to the suction air passage 36 through the fuel passage 37a.
The secondary pressure governor E includes a diaphragm 40 held between the lower wall of the body 35 and a bottom plate 39 so as to define the constant-pressure fuel chamber 38 on the upper side of the diaphragm 40 and an air chamber on the lower side thereof. The constant-pressure fuel chamber 38 is provided with a lever 41 supported by a shaft 42. The left end of the lever 41 is engaged with the diaphragm 40, and the right end of the lever 41 is engaged with the valve element 44. The valve element 44 is urged by a spring 43 to close the fuel inlet passage 44a. When the fuel in the constant-pressure fuel chamber 38 is reduced in quantity and the fuel pressure is decreased, the lever 41 is turned clockwise by the diaphragm 40 acted upon by atmospheric pressure, so that the valve element 44 opens the inlet passage 44a to replenish fuel to the constant-pressure fuel chamber 38. The constant-pressure fuel chamber 38 opens the fuel passage 37a to the suction air passage 36.
An oil passage 34 opens into the suction air passage 36 to lubricate the engine. The oil passage 34 communicates with a transparent tube 33 connected to the upper wall of the body 35. The transparent tube 33 supports a valve casing 32 for an oil regulating valve D. A needle valve 31 threadedly supported by the valve chest 32a of the valve casing 32 regulates the quantity of oil flowing from the lower end outlet of the valve chest 32a to the transparent tube 33. Further, the oil from an oil tank 61 is supplied under pressure to the oil chest 32a through an outlet pipe 63 and pipe 45. For this purpose, pressurized air is supplied from an air pump F to the oil tank 61 through an inlet 62.
Next, the operation of the fuel apparatus for an engine configured as described above will be explained. When the engine B is running, the cooling air sent from the blower in the fan case 22 to the cylinder body 20 strikes a cover 18, and cools the cylinder body 20 when flowing in the substantially horizontal direction from the back to the front of the engine. When the cooling air is heated and discharged from the cover 18 at the front of the engine, the air heats the vaporizer 7. The liquid fuel from the liquefied gas vessel 3 is heated and vaporized by the vaporizer 7, entering the fuel chamber 11 of the primary pressure governor A through the inlet 12. When the pressure of fuel in the fuel chamber 11 becomes higher than a predetermined value, the valve element 8 closes the inlet 12 to keep the pressure of fuel in the fuel chamber 11 almost constant.
The fuel in the fuel chamber 11 enters the constant pressure fuel chamber 38 of the secondary pressure governor E through the valve element 44. When the pressure of fuel in the constant-pressure fuel chamber 38 increases, the diaphragm 40 is pushed down. The lever 41 subjected to the force of the spring 43 is turned by the diaphragm 40 to close the valve element 44, so that the pressure of fuel in the constant-pressure fuel chamber 38 is kept almost constant. The fuel in the constant-pressure fuel chamber 38 passes through the passage 37, and is mixed with the air in the suction air passage 36, and further sucked into the combustion chamber of the engine while being mixed with the oil from the oil passage 34.
The conventional gas engine shown in FIG. 8 is constructed so that the vaporizer 7 for vaporizing the liquid fuel is disposed close to the cylinder body 20 of the engine, and is subjected to the high-temperature cooling air after the cooling of the cylinder body, so that liquid fuel passing through the vaporizer is heated. The liquid fuel is vaporized completely when the outside air temperature is high as in the summer. However, in the winter or in other cases when the outside air temperature is lower than about 16, there is often insufficient heating of the fuel, so that often the liquid fuel is not vaporized completely.
When this happens, liquid fuel flows into the mixer, and therefore the mixer malfunctions, causing the engine to stop.